Suitability of Carbazolyl Hauser and Turbo-Hauser Bases as Magnesium-Based Electrolytes

Lithium-ion batteries pose certain drawbacks and alternatives are highly demanded. Requirements such as low corrosiveness, electrochemical stability and suitable electrolytes can be met by magnesium-ion batteries. Metalation of carbazole with Mg in THF in the presence of ethyl bromide yields the sparingly soluble Hauser base [(thf)(3)Mg(Carb)Br] (1) which shows a Schlenk-type equilibrium with formation of [(thf)(3)Mg(Carb)(2)] and [(thf)(4)MgBr2]. A THF solution of 1 shows a low over-potential and a good cyclability of electrodeposition/-stripping of Mg on a Cu current collector. An improved performance is achieved with the turbo-Hauser bases [(thf)(Carb)Mg(mu-Br/X)(2)Li(thf)(2)] (X=Br (2) and Cl (3)) which show a significantly higher solubility in ethereal solvents. The THF solvation energies increase from (thf)(x)MgBr2 over (thf)(x)Mg(Carb)Br to (thf)(x)Mg(Carb)(2) for an equal number x of ligated THF molecules.